The month is wrapping up, and tomorrow we start a new featured topic. It’s that time, once again, to thank all of the wonderful people who contributed guest articles and participated in interviews with us here on the site.
Thanks again, one and all.
Remember that we are always open to guest contributions, both on and off topic. If you have something you’d like to share with the community, contact shaun [at] designingsound [dot] org. Tomorrow begins a focus on the intersection of sound design and music.
Guest contribution by Owen Green
[This is the second of a two part series on loudness, mixing, metering and the new ITU loudness spec]
The New Loudness Standards, and What They Might Mean for Us
Depending on the field in which one worked, standard production practices have tended to be orientated around peak normalisation of material. That is, lining up recordings by their peak level; in music, recordings are now often lined right up 0 dBfs; in broadcast a common specification is to peak at -9 dBfs (which allows some headroom in recognition of the fact that analogue QPPMs don’t truly measure signal peaks). As is hopefully clear from last week’s article, this has almost no bearing on how loud we perceive the material to be.
A set of new recommendations has been developed since 2006, and are now becoming standard or legally stipulated practice in some industry areas and countries. It is therefore worthwhile to get a handle on what they mean, and how to use them as soon as possible.
The core proposal comes in the form of a recommendation from the ITU (International Telecommunications Union) on how to measure the loudness of a signal (ITU BS.1770-2). Local bodies, such as the EBU in Europe and ATSC in the US, have then published (pretty similar) guidelines on working practices derived from the ITU spec. The common thrust of these proposals (actually, now rules in some places!) is that they enable a move away from normalising by peaks to normalising by (approximate) loudness:
So, material that has been more compressed in dynamic range (so as to appear louder when peak normalised) loses its ‘advantage’ by being reduced in gain
so that its perceived loudness is on par with more dynamic material.